Non-Fermi liquid ground states in strongly correlated f-electron materials (invited) (abstract)

Abstract

Strongly correlated electron materials, especially the high transition temperature (Tc) cuprate superconductors and heavy fermion rare earth and actinide compounds, have been the focus of intense investigation in recent years. The unusual normal state properties of the high Tc cuprates have been ascribed by some researchers to a non-Fermi liquid (NFL) metallic state, while the anomalous properties of certain heavy fermion U-based superconductors such as UBe13 have been attributed to NFL behavior due to a two-channel quadrupolar Kondo effect. Although NFL behavior has not been established in any of the U-based heavy fermion superconductors, evidence for its occurrence in an f-electron material has been found in the U alloy system Y1−xUxPd3. Subsequently, NFL behavior was observed in a number of other f-electron alloy systems, including Sc1−xUxPd3, UCu3.5Pd1.5, Th0.1U0.9Be13, Th1−xUxRu2Si2 (x≤0.07), Th1−xUxPd2Al3, La0.9Ce0.1Cu2Si2, and CeCu5.9Au0.1. Evidence for NFL behavior in Y1−xUxPd3 and related systems is reviewed and discussed within the context of possible microscopic mechanisms. Some systematics of the NFL low temperature behavior observed in several f-electron materials include a linear temperature dependence of the electrical resistivity ρ∼1−aT with the coefficient a either ≳0 or <0, a logarithmically diverging specific heat C/T∼−ln T, and T1/2 asymptotic behavior of the magnetic susceptibility χ∼1−T1/2.